A method and system for image acquisition of pulsed arc welding

Abstract

The present application provides a kind of image acquisition method and system of pulse arc welding, wherein the method comprises: obtaining light signal intensity, which is the intensity of arc light in the pulse arc welding, expressed as an electrical signal;Pre-set empirical threshold, when the light signal intensity is lower than the empirical threshold, it is inferred that it can be taken;The master chip collects the light signal intensity expressed by the electrical signal according to the preset frequency;When the signal trigger condition is met, that is, the light signal intensity reaches the preset cycle point, a trigger signal is sent out, and after a delay shooting time t (t≥0), the camera takes a picture, which should ensure that the light signal intensity is lower than the preset empirical threshold when shooting. Using this method, the moment when the arc light is strong can be avoided, and then a relatively clear photo when the arc light is weak can be captured, which facilitates subsequent analysis, reduces the burden on the system, improves efficiency, saves storage space, and has excellent effect.

Description

Technical Field

[0001] This invention relates to a welding robot weld seam trajectory tracking and visual sensing technology, and more particularly to an image acquisition method and system for pulsed arc welding. Background Technology

[0002] Arc welding, as a fundamental metal processing method, is widely used in various sectors of the national economy. Pulsed arc welding, in particular, utilizes two different currents—a basic current and a pulsed current—resulting in a lower average current value and less total heat generation throughout the welding process. This not only reduces the heat-affected zone and effectively controls welding deformation, but also increases the peak current with less total heat generation, promoting stable droplet transfer while simultaneously shrinking and cooling the molten pool. This is beneficial for welding easily deformable structures and is highly advantageous for all-position welding, making it a crucial guarantee for achieving advanced welding processes and obtaining high-quality weld joints.

[0003] With the development of welding technology, the automation level of the welding process is constantly improving. Traditional welding was done manually, but welding robots have replaced manual labor, effectively improving both precision and efficiency. Currently, the development of intelligent technology and the demand for intelligent welding have driven research into real-time monitoring, feedback, and automatic adjustment of the welding process; weld seam trajectory tracking is one such research direction.

[0004] Visual sensing technology acquires weld seam images and transforms environmental information into recognizable positional and welding process information, thereby controlling the welding process. However, due to numerous factors during welding, such as spatter and especially arc light, the acquired weld seam images often contain a significant amount of noise. Low image quality greatly complicates subsequent analysis, increases the system's workload, is time-consuming and space-intensive, and yields unsatisfactory results. Summary of the Invention

[0005] The technical problem this invention aims to solve is that during pulsed arc welding, the arc light and spatter change periodically with the pulse, causing the image acquisition quality to fluctuate periodically. If the camera takes pictures when both arc light and spatter are strong, the resulting low image quality not only fails to support weld seam tracking technology but also places an additional burden on the system. Therefore, it is necessary to monitor the arc light signal to identify moments when the arc light and corresponding spatter are low, in order to acquire a clearer image of the molten pool.

[0006] In a first aspect, embodiments of the present invention provide an image acquisition method for pulsed arc welding, the method comprising:

[0007] The intensity of the optical signal is obtained, which is represented by an electrical signal and is the intensity of the arc light in the pulsed arc welding.

[0008] The main control chip collects the intensity of the optical signal represented by the electrical signal at a preset frequency.

[0009] A preset empirical threshold is set. When the intensity of the light signal is lower than the preset empirical threshold, it is assumed that a photo can be taken.

[0010] When the signal triggering condition is met, that is, when the light signal intensity reaches the preset period point, a trigger signal is issued. After a delayed shooting time t (t≥0), the camera takes a picture. The delayed shooting time t (t≥0) should ensure that the light signal intensity is lower than the preset empirical threshold when the picture is taken.

[0011] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention, wherein the main control chip is a microcontroller, acquires the intensity of the optical signal represented by the electrical signal, including:

[0012] The microcontroller continuously monitors the electrical signal on the pin and converts the analog signal into a digital signal through the analog-to-digital data conversion module.

[0013] The digital signal is directly transmitted to the memory via the data transmission module.

[0014] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention satisfies the signal triggering condition, that is, the light signal intensity reaches the preset period point, and the main control chip detects that the electrical signal is decreasing and that some or all of the effective sampling points are below the preset empirical threshold, including:

[0015] The main control chip calculates the average value once for every M samples (M≥1) to obtain a valid sampling point.

[0016] When the number of consecutive N (N≥2) valid sampling points decreases, it is determined that the electrical signal is decreasing.

[0017] When the electrical signal decreases, it is determined whether the N consecutive valid sampling points are partially or completely less than the preset empirical threshold. When the determination is yes, the signal triggering condition is met.

[0018] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention acquires the intensity of the optical signal, including:

[0019] The optical signal is converted into an electrical signal, i.e., a current signal, by a photodiode.

[0020] The current signal is amplified by an amplifier to obtain an amplified signal.

[0021] The amplified signal is then low-pass filtered to obtain a low-frequency electrical signal.

[0022] The low-frequency electrical signal is divided to obtain the intensity of the optical signal.

[0023] In some embodiments, the present invention provides an image acquisition method for pulsed arc welding, wherein a convex lens is located between the photodiode and the arc light, and the photodiode is located at the focal point of the convex lens.

[0024] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention uses a convex lens with a focal length of 10-100mm, preferably 20mm.

[0025] In some embodiments, the present invention provides an image acquisition method for pulsed arc welding, wherein the photodiode has a light-shielding plate in a direction other than facing the arc light.

[0026] In some embodiments, the pulse arc welding image acquisition method provided by the present invention further includes:

[0027] Filtering: The arc light in the pulsed arc welding is filtered using a filter between the arc light and the camera.

[0028] In some embodiments, the present invention provides an image acquisition method for pulsed arc welding, wherein the filter is a bandpass filter.

[0029] Secondly, embodiments of the present invention provide an image acquisition system for pulsed arc welding, the system comprising:

[0030] The optical signal intensity acquisition module is used to acquire the optical signal intensity, which is represented by an electrical signal and is the intensity of the arc light in the pulse arc welding.

[0031] The optical signal intensity acquisition module is used to acquire the intensity of the optical signal represented by the electrical signal at a preset frequency.

[0032] The preset experience threshold module is used to preset an experience threshold. When the intensity of the light signal is lower than the experience threshold, it is assumed that a photo can be taken.

[0033] The signal triggering module is used to issue a trigger signal when the signal triggering condition is met, that is, when the light signal intensity reaches a preset periodic point. After a delayed shooting time t (t≥0), the camera takes a picture. The delayed shooting time t (t≥0) should ensure that the light signal intensity is lower than the preset empirical threshold when the picture is taken.

[0034] The camera is used to take a picture after a delay time t, when it receives the trigger signal from the signal trigger module.

[0035] In some embodiments, the pulsed arc welding image acquisition system provided by the present invention uses a microcontroller as the main control chip to acquire the intensity of the optical signal represented by the electrical signal. The optical signal intensity acquisition module includes:

[0036] The analog-to-digital module is used to enable the microcontroller to continuously detect the electrical signal on the pin and convert the analog signal into a digital signal through the analog-to-digital data conversion module.

[0037] The transmission module is used to directly transmit the digital signal to the memory via the data transmission module.

[0038] In some embodiments, the pulsed arc welding image acquisition system provided by the present invention includes a signal triggering module in which the signal triggering condition is met, namely, the intensity of the optical signal reaches a preset periodic point, and the main control chip detects that the electrical signal is decreasing and that some or all of the effective sampling points are less than the empirical threshold. The signal triggering module includes:

[0039] The sampling module is used to calculate the average value once every M samples (M≥1) of the optical signal intensity acquisition module to obtain a valid sampling point;

[0040] The electrical signal decline judgment module is used to determine that the electrical signal is declining when N consecutive (N≥2) valid sampling points show a decrease.

[0041] The low threshold judgment module is used to determine whether the N consecutive valid sampling points are partially or completely less than the empirical threshold when the electrical signal is decreasing. When the judgment is yes, the signal triggering condition is met.

[0042] In some embodiments, the pulsed arc welding image acquisition system provided by the present invention includes an optical signal intensity acquisition module comprising:

[0043] A photodiode is used to convert optical signals into electrical signals, i.e., current signals.

[0044] An amplifier is used to amplify the current signal to obtain an amplified signal.

[0045] A low-pass filter is used to filter the amplified signal to obtain a low-frequency electrical signal.

[0046] A voltage divider is used to divide the low-frequency electrical signal to obtain the intensity of the optical signal.

[0047] In some embodiments, the pulse arc welding image acquisition system provided by the present invention further includes:

[0048] A convex lens is positioned between the photodiode and the arc light, with the photodiode located at the focal point of the convex lens.

[0049] In some embodiments, the pulse arc welding image acquisition system provided by the present invention has a convex lens with a focal length of 10-100mm, preferably 20mm.

[0050] In some embodiments, the pulse arc welding image acquisition system provided by the present invention further includes:

[0051] A light-shielding plate, which is located in a direction where the photodiode is not facing the arc light.

[0052] In some embodiments, the pulse arc welding image acquisition system provided by the present invention further includes:

[0053] A filter is used to filter the arc light in the pulsed arc welding, and the filter is placed between the arc light and the camera.

[0054] In some embodiments, the present invention provides an image acquisition system for pulsed arc welding, wherein the filter is a bandpass filter.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] This invention uses the actual changes in light intensity as a reference, converting optical signals into electrical signals in real time. The main control chip samples the analog electrical signals at a certain frequency. Changes in the intensity of the arc light cause the electrical signal to strengthen or weaken. Therefore, by setting an empirical threshold, the program in the main control chip can issue a trigger signal when the analog electrical signal is detected at a preset position within the pulse cycle. After triggering, the camera immediately or after a specified delay takes a picture, thus avoiding the moment when the arc light is strongest and capturing a clearer picture when the arc light is weaker. This greatly facilitates subsequent analysis, reduces the system load, improves efficiency, saves space, and achieves excellent results. This invention can further meet the requirements of intelligent technology for the intelligence of welding, and promotes research on real-time monitoring, feedback, and automatic adjustment of the welding process. Attached Figure Description

[0057] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a flowchart of a specific embodiment of the pulse arc welding image acquisition system of the present invention.

[0059] Figure 2 This is a system structure diagram of a specific embodiment of the pulse arc welding image acquisition method of the present invention.

[0060] Figure 3 This is a simplified schematic diagram of a specific embodiment of the pulsed arc welding image acquisition method of the present invention. Detailed Implementation

[0061] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Those skilled in the art should understand that the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments in this application, those skilled in the art can make any appropriate modifications or variations to obtain all other embodiments.

[0062] In a first aspect, embodiments of the present invention provide an image acquisition method for pulsed arc welding, the method comprising:

[0063] The intensity of the optical signal is obtained, which is represented by an electrical signal and is the intensity of the arc light in the pulsed arc welding.

[0064] The main control chip collects the intensity of the optical signal represented by the electrical signal at a preset frequency.

[0065] A preset empirical threshold is set. When the intensity of the light signal is lower than the preset empirical threshold, it is assumed that a photo can be taken.

[0066] When the signal triggering condition is met, that is, when the light signal intensity reaches the preset period point, a trigger signal is issued. After a delay time t (t≥0), the camera takes a picture. The delay time t (t≥0) should ensure that the light signal intensity is lower than the preset empirical threshold when the picture is taken.

[0067] In this embodiment, the step of converting optical signals to electrical signals is... Figure 1 It is not shown in the flowchart, but Figure 2 A light signal intensity acquisition module that performs this function is shown. This embodiment includes, but is not limited to, [other functions]. Figure 2 The right side of the text details this step, as it can be implemented using various light-sensitive sensors, such as photoresistors, photodiodes, phototransistors, optocouplers, and photovoltaic cells. Figure 1 As shown, this embodiment also includes a step of acquiring the intensity of the light signal, corresponding to... Figure 2 The optical signal intensity acquisition module. This embodiment includes, but is not limited to, the optical signal intensity acquisition module. Figure 1 , Figure 2 The details of this step are as follows. This step can be implemented using different methods depending on the signal acquisition requirements of the main control chip. The main control chip can be a PLC or a microcontroller. The main control chip acquires the electrical signal at a preset frequency, such as 500kHz. Figure 2 The optical signal intensity acquisition module in the system includes some of the functions of the main control chip. For example... Figure 1 As shown, this embodiment also includes signal triggering and camera capturing steps, corresponding to Figure 2The system includes a signal triggering module and a camera. In pulsed arc welding, because the pulse appears periodically at a fixed frequency, the detected electrical signal also exhibits corresponding periodic characteristics. Therefore, when the intensity of the detected light signal reaches a specified position within the period, a trigger signal is emitted. This ensures that after a delayed imaging time t (t≥0), when the camera takes a picture, the intensity of the light signal is just below a preset empirical threshold, meaning the arc is in a weaker period. The captured image is less affected by the arc and therefore clearer, reducing the workload of post-processing. This preset periodic point only needs to be identifiable during detection; the trigger signal is emitted when this point is reached. This embodiment includes, but is not limited to, [the following is not explicitly stated in the original text]. Figure 1 , Figure 2 The detailed section on this step is as follows. This step can be accomplished in several ways. For example, summing 10 consecutive data points together, calculating the difference between the sums of adjacent data sets, using the change in this difference to determine the change in signal strength, and then determining the position within the cycle based on the magnitude of the sum of each data set. The key points of this step are: first, to eliminate numerical errors caused by random factors; and second, to ensure that the changes in the calculated values ​​reflect the periodic changes in optical signal strength and that the position within the cycle can be determined based on the magnitude of the values. Figure 2 The function of the preset experience threshold module is in Figure 1 It is included but not directly shown. The value of the elapsed delayed shooting time t (t≥0) can be preset manually or using empirical formulas, or it can be calculated by the main control chip according to a given algorithm, as long as the arc light is weak during shooting and a qualified image can be obtained. This value can be set before the system is turned on, or it can be adjusted as needed during operation. This value can be set at the camera end or at the main control chip end. This module is in Figure 2 The location of this module in the code only indicates that the system includes it; however, the order in which this module functions is not affected by the system's limitations. Figure 2 Restrictions. Figure 1 , Figure 2 The camera shown is an industrial camera or camera module, which can be a CCD camera or a CMOS camera. The camera's shooting mode can be configured, set to external trigger mode, and output a rising or falling edge signal to the camera to selectively take a picture at a specific time. The camera's configuration and image transmission can be controlled by the main control chip or by external software. Figure 1 As shown, the process described in this embodiment is continuously repeated, thus continuously obtaining qualified images.

[0068] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention, wherein the main control chip is a microcontroller, acquires the intensity of the optical signal represented by the electrical signal, including:

[0069] The microcontroller continuously monitors the electrical signal on the pin and converts the analog signal into a digital signal through the analog-to-digital data conversion module.

[0070] The digital signal is directly transmitted to the memory via the data transmission module.

[0071] In this embodiment, the main control chip is a microcontroller (MCU), which can be connected to the required peripherals. For example, an STM32F103R8T6 microcontroller can be selected. This microcontroller has comprehensive peripheral functions and is stable and efficient in industrial products. After connecting the analog-to-digital converter (AD) module and the data transfer module (DMA) module to this microcontroller, the operating mode and parameters of the peripherals can be configured by setting the peripheral registers to meet the needs of actual industrial production applications. Figure 1 As shown, the microcontroller continuously detects the analog signals on the pins and uses the microcontroller's peripheral analog-to-digital (AD) converter to continuously convert the analog signals into digital signals, i.e., performing AD polling conversion. Sampling is done every certain number of clock cycles, such as once every 239 clock cycles. Then, the data transfer (DMA) module directly transfers the digital signal converted by the AD converter to the memory, i.e., performing DMA transfer, saving the computation time overhead of the main control chip. In this embodiment, the module that implements these two steps is... Figure 2 The analog-to-digital (A / D) module and the data transfer (DMA) module refer to the combination of hardware and software that implement these two specific functions. The A / D module and the DMA module are two hardware components that are external peripherals connected to the microcontroller.

[0072] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention satisfies the signal triggering condition, that is, the light signal intensity reaches the preset period point, and the main control chip detects that the electrical signal is decreasing and that some or all of the effective sampling points are below the preset empirical threshold, including:

[0073] The main control chip calculates the average value once for every M samples (M≥1) to obtain a valid sampling point.

[0074] When the number of consecutive N (N≥2) valid sampling points decreases, it is determined that the electrical signal is decreasing.

[0075] When the electrical signal decreases, it is determined whether the N consecutive valid sampling points are partially or completely less than the preset empirical threshold. When the determination is yes, the signal triggering condition is met.

[0076] In this embodiment, as Figure 1As shown, the main control chip is responsible for inspecting and collecting electrical signals, then performing mean smoothing on the signals to achieve cyclic interval sampling, and placing valid sampling points into the sampling queue. Next, the sampling points in the sampling queue are judged for signal decline according to the falling edge judgment rule. The falling edge judgment rule is that when the electrical signal values ​​of the sampling points in the sampling queue decrease sequentially, a falling edge is presumed. When a falling edge is determined, a low threshold judgment is performed. The low threshold judgment rule is that when the electrical signal values ​​of the sampling points are partially or entirely less than a preset empirical threshold, the electrical signal is presumed to have entered the low threshold region, suitable for image acquisition. When the electrical signal is determined to have entered the low threshold region, a trigger signal is issued, instructing the camera to take a picture. The camera executes the picture command after a delay of t (t≥0). Specifically, assuming a sampling frequency of 500kHz, the average of ten voltage values ​​is calculated as one valid sampling point. This cyclic sampling is repeated to obtain four valid sampling points. When the values ​​of the four tests show a decreasing trend and are partially or all below the preset empirical threshold, it ensures that the sampling position is at a specific position in the waveform. At this time, a trigger signal is issued, and after a delay time t (t≥0), the camera takes a picture, thereby eliminating external signal interference and obtaining a relatively ideal shooting effect.

[0077] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention acquires the intensity of the optical signal, including:

[0078] The optical signal is converted into an electrical signal, i.e., a current signal, by a photodiode.

[0079] The current signal is amplified by an amplifier to obtain an amplified signal.

[0080] The amplified signal is then low-pass filtered to obtain a low-frequency electrical signal.

[0081] The low-frequency electrical signal is divided to obtain the intensity of the optical signal.

[0082] In this embodiment, as Figure 2As shown, the optical signal intensity acquisition module includes a photodiode, an amplifier, a low-pass filter, and a voltage divider. The photodiode converts the optical signal into an electrical signal, i.e., a current signal. A photodiode is a device used to collect arc energy; it is a photoelectric sensor that converts optical signals into electrical signals. The core component of the diode is the PN junction. When a forward voltage is applied to the PN junction, its resistance is very small, allowing a large forward current to pass through. In this embodiment, the diode is placed under a reverse operating voltage. Initially, when the arc light is weak, only a very small amount of reverse saturation current passes through, and the circuit is essentially in a cutoff state. As the arc light intensifies, the reverse current rapidly increases to tens of microamps. The reverse current signal is amplified by the amplifier, then passed through a low-pass filter to filter out some mixed high-frequency signals, and finally, after voltage division, the optical signal intensity is obtained and output to the pin of the main control chip for acquiring analog signals.

[0083] When using the technical solutions of this invention in combination, such as when the main control chip in this embodiment is a microcontroller with peripherals, the light signal intensity obtained by the photoelectric signal acquisition and conversion module is input to the pin of the microcontroller for acquiring analog signals, such as... Figure 1 As shown, the analog-to-digital (A / D) converter converts the signal into a digital signal, which is then transferred to memory via the data transfer (DMA) module, completing the signal acquisition and transmission phase. After signal acquisition and transmission, data processing is performed. For example... Figure 1 As shown, the data needs to go through steps such as mean smoothing, electrical signal decline judgment, and low threshold judgment. Figure 3 A simpler diagram is provided. Figure 3 Data acquisition and transmission on the left are primarily handled by hardware, while data processing on the right is mainly implemented by software. Essentially, both data acquisition and transmission, and data processing, are accomplished through a combination of hardware and software. The microcontroller samples M times (M≥1), calculates the average, and obtains a valid sampling point, thus performing mean smoothing on the data. When N consecutive (N≥2) valid sampling points show a decreasing trend, it is determined that the electrical signal is declining, and the data is processed according to the falling edge judgment rule. After detecting a declining electrical signal, the values ​​of the valid sampling points are compared with a preset empirical threshold, i.e., the data is processed according to the low threshold judgment rule. When all values ​​are below the preset empirical threshold, a trigger signal is issued. After the trigger signal is issued, a delay of t (t≥0) is allowed, allowing the arc light to be in a weak state at the time of image capture, at which point the camera takes the picture. Figure 1 As shown, this process repeats continuously, thus continuously obtaining qualified images.

[0084] In some embodiments, the present invention provides an image acquisition method for pulsed arc welding, wherein a convex lens is located between the photodiode and the arc light, and the photodiode is located at the focal point of the convex lens.

[0085] In this embodiment, in order to increase the signal-to-noise ratio of the optical signal (arc signal: background light signal), a convex lens or a group of convex lenses is placed in front of the diode to focus the arc signal onto the diode to enhance the intensity of the arc signal.

[0086] In some embodiments, the pulsed arc welding image acquisition method provided by the present invention uses a convex lens with a focal length of 10-100mm, preferably 20mm.

[0087] In this embodiment, in order to maintain good performance while occupying less space, the focal length of the convex lens is between 10 and 100 mm, preferably 20 mm.

[0088] In some embodiments, the present invention provides an image acquisition method for pulsed arc welding, wherein the photodiode has a light-shielding plate in a direction other than facing the arc light.

[0089] In this embodiment, to increase the signal-to-noise ratio of the optical signal (arc signal: background light signal), a light-shielding plate is placed around the diode to block the background light and reduce the intensity of the background light signal. There are no specific limitations on the area, size, or orientation of the light-shielding plate, as long as it can block part of the background light so that the signal intensity of the background light is low enough to identify or clearly identify the intensity of the arc signal.

[0090] In some embodiments, the pulse arc welding image acquisition method provided by the present invention further includes:

[0091] Filtering: The arc light in the pulsed arc welding is filtered using a filter between the arc light and the camera.

[0092] In this embodiment, as Figure 2 As shown, a filter is placed between the arc light and the camera. A filter is made by adding special dyes to a plastic or glass substrate or by depositing an optical film on its surface. It is used to attenuate (absorb) certain wavelengths of light or to precisely select a small range of wavelengths to pass through, while reflecting (or absorbing) other unwanted wavelengths. Using filters can optimize photographic results.

[0093] In some embodiments, the present invention provides an image acquisition method for pulsed arc welding, wherein the filter is a bandpass filter.

[0094] In this embodiment, preferably, the filter is a bandpass filter, which allows light signals to pass through in a specific wavelength band, while light signals on both sides deviating from this wavelength band are blocked.

[0095] Secondly, embodiments of the present invention provide an image acquisition system for pulsed arc welding, the system comprising:

[0096] The optical signal intensity acquisition module is used to acquire the optical signal intensity, which is represented by an electrical signal and is the intensity of the arc light in the pulse arc welding.

[0097] The optical signal intensity acquisition module is used to acquire the intensity of the optical signal represented by the electrical signal at a preset frequency.

[0098] The preset experience threshold module is used to preset an experience threshold. When the intensity of the light signal is lower than the experience threshold, it is assumed that a photo can be taken.

[0099] The signal triggering module is used to issue a trigger signal when the signal triggering condition is met, that is, when the light signal intensity reaches a preset periodic point. After a delayed shooting time t (t≥0), the camera takes a picture. The delayed shooting time t (t≥0) should ensure that the light signal intensity is lower than the preset empirical threshold when the picture is taken.

[0100] The camera is used to take a picture after a delay time t, when it receives the trigger signal from the signal trigger module.

[0101] In this embodiment, the step of converting optical signals to electrical signals is... Figure 1 It is not shown in the flowchart, but Figure 2 A light signal intensity acquisition module that performs this function is shown. This embodiment includes, but is not limited to, [other functions]. Figure 2 The right side of the text details this step, as it can be implemented using various light-sensitive sensors, such as photoresistors, photodiodes, phototransistors, optocouplers, and photovoltaic cells. Figure 1 As shown, this embodiment also includes a step of acquiring the intensity of the light signal, corresponding to... Figure 2 The optical signal intensity acquisition module. This embodiment includes, but is not limited to, the optical signal intensity acquisition module. Figure 1 , Figure 2 The details of this step are as follows. This step can be implemented using different methods depending on the signal acquisition requirements of the main control chip. The main control chip can be a PLC or a microcontroller. The main control chip acquires the electrical signal at a preset frequency, such as 500kHz. Figure 2 The optical signal intensity acquisition module in the system includes some of the functions of the main control chip. For example... Figure 1 As shown, this embodiment also includes signal triggering and camera capturing steps, corresponding to Figure 2The system includes a signal triggering module and a camera. In pulsed arc welding, because the pulses occur periodically at a fixed frequency, the detected electrical signal also exhibits corresponding periodic characteristics. Therefore, when the intensity of the detected light signal reaches a specified position within the period, a trigger signal is emitted. This ensures that after a delayed imaging time t (t≥0), when the camera takes a picture, the intensity of the light signal is just below a preset empirical threshold, meaning the arc is in a weaker period. The captured image is less affected by the arc and therefore clearer, reducing the workload of post-processing. This preset periodic point only needs to be identifiable during detection; the trigger signal is emitted when this point is reached. This embodiment includes, but is not limited to, [the following is not explicitly stated in the original text]. Figure 1 , Figure 2 The detailed section on this step is as follows. This step can be accomplished in several ways. For example, summing 10 consecutive data points together, calculating the difference between the sums of adjacent data sets, using the change in this difference to determine the change in signal strength, and then determining the position within the cycle based on the magnitude of the sum of each data set. The key points of this step are: first, to eliminate numerical errors caused by random factors; and second, to ensure that the changes in the calculated values ​​reflect the periodic changes in optical signal strength and that the position within the cycle can be determined based on the magnitude of the values. Figure 2 The function of the preset experience threshold module is in Figure 1 It is included but not directly shown. The value of the elapsed delayed shooting time t (t≥0) can be preset manually or using empirical formulas, or it can be calculated by the main control chip according to a given algorithm, as long as the arc light is weak during shooting and a qualified image can be obtained. This value can be set before the system is turned on, or it can be adjusted as needed during operation. This value can be set at the camera end or at the main control chip end. This module is in Figure 2 The location of this module in the code only indicates that the system includes it; however, the order in which this module functions is not affected by the system's limitations. Figure 2 Restrictions. Figure 1 , Figure 2 The camera shown is an industrial camera or camera module, which can be a CCD camera or a CMOS camera. The camera's shooting mode can be configured, set to external trigger mode, and output a rising or falling edge signal to the camera to selectively take a picture at a specific time. The camera's configuration and image transmission can be controlled by the main control chip or by external software. Figure 1 As shown, the process described in this embodiment is continuously repeated, thus continuously obtaining qualified images.

[0102] In some embodiments, the pulsed arc welding image acquisition system provided by the present invention uses a microcontroller as the main control chip to acquire the intensity of the optical signal represented by the electrical signal. The optical signal intensity acquisition module includes:

[0103] The analog-to-digital module is used to enable the microcontroller to continuously detect the electrical signal on the pin and convert the analog signal into a digital signal through the analog-to-digital data conversion module.

[0104] The transmission module is used to directly transmit the digital signal to the memory via the data transmission module.

[0105] In this embodiment, the main control chip is a microcontroller (MCU), which can be connected to the required peripherals. For example, an STM32F103R8T6 microcontroller can be selected. This microcontroller has comprehensive peripheral functions and is stable and efficient in industrial products. After connecting the analog-to-digital converter (AD) module and the data transfer module (DMA) module to this microcontroller, the operating mode and parameters of the peripherals can be configured by setting the peripheral registers to meet the needs of actual industrial production applications. Figure 1 As shown, the microcontroller continuously detects the analog signals on the pins and uses the microcontroller's peripheral analog-to-digital (AD) converter to continuously convert the analog signals into digital signals, i.e., performing AD polling conversion. Sampling is done every certain number of clock cycles, such as once every 239 clock cycles. Then, the data transfer (DMA) module directly transfers the digital signal converted by the AD converter to the memory, i.e., performing DMA transfer, saving the computation time overhead of the main control chip. In this embodiment, the module that implements these two steps is... Figure 2 The analog-to-digital (A / D) module and the data transfer (DMA) module refer to the combination of hardware and software that implement these two specific functions. The A / D module and the DMA module are two hardware components that are external peripherals connected to the microcontroller.

[0106] In some embodiments, the pulsed arc welding image acquisition system provided by the present invention includes a signal triggering module in which the signal triggering condition is met, namely, the intensity of the optical signal reaches a preset periodic point, and the main control chip detects that the electrical signal is decreasing and that some or all of the effective sampling points are less than the empirical threshold. The signal triggering module includes:

[0107] The sampling module is used to calculate the average value once every M samples (M≥1) of the optical signal intensity acquisition module to obtain a valid sampling point;

[0108] The electrical signal decline judgment module is used to determine that the electrical signal is declining when N consecutive (N≥2) valid sampling points show a decrease.

[0109] The low threshold judgment module is used to determine whether the N consecutive valid sampling points are partially or completely less than the empirical threshold when the electrical signal is decreasing. When the judgment is yes, the signal triggering condition is met.

[0110] In this embodiment, as Figure 1 As shown, the main control chip is responsible for inspecting and collecting electrical signals, then performing mean smoothing on the signals to achieve cyclic interval sampling, and placing valid sampling points into the sampling queue. Next, the sampling points in the sampling queue are judged for signal decline according to the falling edge judgment rule. The falling edge judgment rule is that when the electrical signal values ​​of the sampling points in the sampling queue decrease sequentially, a falling edge is presumed. When a falling edge is determined, a low threshold judgment is performed. The low threshold judgment rule is that when the electrical signal values ​​of the sampling points are partially or entirely less than a preset empirical threshold, the electrical signal is presumed to have entered the low threshold region, suitable for image acquisition. When the electrical signal is determined to have entered the low threshold region, a trigger signal is issued, instructing the camera to take a picture. The camera executes the picture command after a delay of t (t≥0). Specifically, assuming a sampling frequency of 500kHz, the average of ten voltage values ​​is calculated as one valid sampling point. This cyclic sampling is repeated to obtain four valid sampling points. When the values ​​of the four tests show a decreasing trend and are partially or all below the preset empirical threshold, it ensures that the sampling position is at a specific position in the waveform. At this time, a trigger signal is issued, and after a delay time t (t≥0), the camera takes a picture, thereby eliminating external signal interference and obtaining a relatively ideal shooting effect.

[0111] In some embodiments, the pulsed arc welding image acquisition system provided by the present invention includes an optical signal intensity acquisition module comprising:

[0112] A photodiode is used to convert optical signals into electrical signals, i.e., current signals.

[0113] An amplifier is used to amplify the current signal to obtain an amplified signal.

[0114] A low-pass filter is used to filter the amplified signal to obtain a low-frequency electrical signal.

[0115] A voltage divider is used to divide the low-frequency electrical signal to obtain the intensity of the optical signal.

[0116] In this embodiment, as Figure 2As shown, the optical signal intensity acquisition module includes a photodiode, an amplifier, a low-pass filter, and a voltage divider. The photodiode converts the optical signal into an electrical signal, i.e., a current signal. A photodiode is a device used to collect arc energy; it is a photoelectric sensor that converts optical signals into electrical signals. The core component of the diode is the PN junction. When a forward voltage is applied to the PN junction, its resistance is very small, allowing a large forward current to pass through. In this embodiment, the diode is placed under a reverse operating voltage. Initially, when the arc light is weak, only a very small amount of reverse saturation current passes through, and the circuit is essentially in a cutoff state. As the arc light intensifies, the reverse current rapidly increases to tens of microamps. The reverse current signal is amplified by the amplifier, then passed through a low-pass filter to filter out some mixed high-frequency signals, and finally, after voltage division, the optical signal intensity is obtained and output to the pin of the main control chip for acquiring analog signals.

[0117] When using the technical solutions of this invention in combination, such as when the main control chip in this embodiment is a microcontroller with peripherals, the light signal intensity obtained by the photoelectric signal acquisition and conversion module is input to the pin of the microcontroller for acquiring analog signals, such as... Figure 1 As shown, the analog-to-digital (A / D) converter converts the signal into a digital signal, which is then transferred to memory via the data transfer (DMA) module, completing the signal acquisition and transmission phase. After signal acquisition and transmission, data processing is performed. For example... Figure 1 As shown, the data needs to go through steps such as mean smoothing, electrical signal decline judgment, and low threshold judgment. Figure 3 A simpler diagram is provided. Figure 3 Data acquisition and transmission on the left are primarily handled by hardware, while data processing on the right is mainly implemented by software. Essentially, both data acquisition and transmission, and data processing, are accomplished through a combination of hardware and software. The microcontroller samples M times (M≥1), calculates the average, and obtains a valid sampling point, thus performing mean smoothing on the data. When N consecutive (N≥2) valid sampling points show a decreasing trend, it is determined that the electrical signal is declining, and the data is processed according to the falling edge judgment rule. After detecting a declining electrical signal, the values ​​of the valid sampling points are compared with a preset empirical threshold, i.e., the data is processed according to the low threshold judgment rule. When all values ​​are below the preset empirical threshold, a trigger signal is issued. After the trigger signal is issued, a delay of t (t≥0) is allowed, allowing the arc light to be in a weak state at the time of image capture, at which point the camera takes the picture. Figure 1 As shown, this process repeats continuously, thus continuously obtaining qualified images.

[0118] In some embodiments, the pulse arc welding image acquisition system provided by the present invention further includes:

[0119] A convex lens is positioned between the photodiode and the arc light, with the photodiode located at the focal point of the convex lens.

[0120] In this embodiment, in order to increase the signal-to-noise ratio of the optical signal (arc signal: background light signal), a convex lens or a group of convex lenses is placed in front of the diode to focus the arc signal onto the diode to enhance the intensity of the arc signal.

[0121] In some embodiments, the pulse arc welding image acquisition system provided by the present invention has a convex lens with a focal length of 10-100mm, preferably 20mm.

[0122] In this embodiment, in order to maintain good performance while occupying less space, the focal length of the convex lens is between 10 and 100 mm, preferably 20 mm.

[0123] In some embodiments, the pulse arc welding image acquisition system provided by the present invention further includes:

[0124] A light-shielding plate, which is located in a direction where the photodiode is not facing the arc light.

[0125] In this embodiment, to increase the signal-to-noise ratio of the optical signal (arc signal: background light signal), a light-shielding plate is placed around the diode to block the background light and reduce the intensity of the background light signal. There are no specific limitations on the area, size, or orientation of the light-shielding plate, as long as it can block part of the background light so that the signal intensity of the background light is low enough to identify or clearly identify the intensity of the arc signal.

[0126] In some embodiments, the pulse arc welding image acquisition system provided by the present invention further includes:

[0127] A filter is used to filter the arc light in the pulsed arc welding, and the filter is placed between the arc light and the camera.

[0128] In this embodiment, as Figure 2 As shown, a filter is placed between the arc light and the camera. A filter is made by adding special dyes to a plastic or glass substrate or by depositing an optical film on its surface. It is used to attenuate (absorb) certain wavelengths of light or to precisely select a small range of wavelengths to pass through, while reflecting (or absorbing) other unwanted wavelengths. Using filters can optimize photographic results.

[0129] In some embodiments, the present invention provides an image acquisition system for pulsed arc welding, wherein the filter is a bandpass filter.

[0130] In this embodiment, preferably, the filter is a bandpass filter, which allows light signals to pass through in a specific wavelength band, while light signals on both sides deviating from this wavelength band are blocked.

Claims

1. An image acquisition method for pulsed arc welding, characterized in that, The welding current in the pulsed arc welding varies periodically, and the method includes: The intensity of the optical signal is acquired in real time, and the intensity of the optical signal is represented by an electrical signal, which is the intensity of the arc light in the pulse arc welding. The main control chip collects the intensity of the optical signal represented by the electrical signal at a preset frequency; A preset empirical threshold is used to presume that an image will be taken when the intensity of the light signal is lower than the preset empirical threshold. When the signal triggering condition is met, that is, when the light signal intensity reaches the preset period point in the current pulse period, a trigger signal is issued. After a delayed shooting time t, the camera takes a picture. The delayed shooting time t should ensure that the light signal intensity is lower than the preset empirical threshold when taking the picture. The delayed shooting time t≥0. The main control chip is a microcontroller that collects the intensity of the optical signal represented by the electrical signal, including: The microcontroller continuously detects the electrical signal on the pin and converts the analog signal into a digital signal through the analog-to-digital data conversion module; The digital signal is directly transmitted to the memory via the data transmission module; Meeting the signal triggering condition, i.e., the optical signal intensity reaching a preset period point, means that the main control chip detects that the electrical signal is decreasing and that some or all of the effective sampling points are less than the empirical threshold, including: The main control chip calculates the average value once every M samples to obtain a valid sampling point, where M≥1; When N consecutive valid sampling points show a decreasing trend, it is determined that the electrical signal is decreasing, where N≥2; When the electrical signal decreases, it is determined whether the N consecutive valid sampling points are partially or completely less than the empirical threshold. When the determination is yes, the signal triggering condition is met. A convex lens is positioned between the photodiode and the arc light, with the photodiode located at the focal point of the convex lens, which has a focal length of 20 mm.

2. The method according to claim 1, characterized in that: Acquiring the intensity of the optical signal includes: The optical signal is converted into the electrical signal, i.e., the current signal, by a photodiode; The current signal is amplified by an amplifier to obtain an amplified signal; The amplified signal is low-pass filtered to obtain a low-frequency electrical signal; The low-frequency electrical signal is divided to obtain the intensity of the optical signal.

3. The method according to claim 2, characterized in that: The photodiode has a light-shielding plate in a direction other than facing the arc light.

4. The method according to any one of claims 1-3, characterized in that, The method further includes: Filtering: The arc light in the pulsed arc welding is filtered using a filter between the arc light and the camera.

5. The method according to claim 4, characterized in that: The filter is a bandpass filter.

6. An image acquisition system for pulsed arc welding, characterized in that, The welding current in the pulsed arc welding varies periodically, and the system includes: The optical signal intensity acquisition module is used to acquire the optical signal intensity in real time. The optical signal intensity is represented by an electrical signal and is the intensity of the arc light in the pulsed arc welding. The optical signal intensity acquisition module is used to acquire the intensity of the optical signal represented by the electrical signal at a preset frequency; the preset empirical threshold module is used to preset an empirical threshold, and when the intensity of the optical signal is lower than the empirical threshold, it is assumed that an image will be taken. The signal triggering module is used to issue a trigger signal when the signal triggering condition is met, that is, when the light signal intensity reaches a preset period point in the current pulse period. After a delayed shooting time t, the camera takes a picture. The delayed shooting time t should ensure that the light signal intensity is lower than the preset empirical threshold when the picture is taken. The delayed shooting time t≥0. The camera is used to take a picture after the delayed picture taking time t has elapsed since receiving the trigger signal from the signal triggering module. The optical signal intensity acquisition module uses a microcontroller as the main control chip to acquire the optical signal intensity represented by the electrical signal. The optical signal intensity acquisition module includes: The analog-to-digital module is used to enable the microcontroller to continuously detect the electrical signal on the pin and convert the analog signal into a digital signal through the analog-to-digital data conversion module. A transmission module is used to directly transmit the digital signal to the memory via a data transmission module; In the signal triggering module, if the signal triggering condition is met, i.e., the optical signal intensity reaches a preset period point, and the main control chip detects that the electrical signal is decreasing and that some or all of the effective sampling points are less than the empirical threshold, the signal triggering module includes: The sampling module is used to calculate the average value once every M samples by the optical signal intensity acquisition module to obtain a valid sampling point, where M≥1; The electrical signal decline judgment module is used to determine that the electrical signal is declining when N consecutive valid sampling points show a decrease, where N≥2; The low threshold judgment module is used to determine whether the N consecutive valid sampling points are partially or completely less than the empirical threshold when the electrical signal is decreasing. When the judgment is yes, the signal triggering condition is met. A convex lens is positioned between the photodiode and the arc light, with the photodiode located at the focal point of the convex lens, which has a focal length of 20 mm.

7. The system according to claim 6, characterized in that: The optical signal intensity acquisition module includes: A photodiode is used to convert optical signals into electrical signals, i.e., current signals. An amplifier is used to amplify the current signal to obtain an amplified signal. A low-pass filter is used to filter the amplified signal to obtain a low-frequency electrical signal. A voltage divider is used to divide the low-frequency electrical signal to obtain the optical signal intensity.

8. The system according to claim 7, characterized in that, The system also includes: A light-shielding plate, wherein the light-shielding plate is in a direction not facing the photodiode toward the arc light.

9. The system according to any one of claims 6-8, characterized in that, The system also includes: A filter is used to filter the arc light in the pulsed arc welding, the filter being between the arc light and the camera.

10. The system according to claim 9, characterized in that: The filter is a bandpass filter.

Images